This application is not referenced in any microfiche appendix.
Previously issued United States Patents that provide background information concerning the technology to which this invention is directed include the following:
Hodgson, U.S. Pat. No. 4,280,867, discloses a reboiler used to heat wet glycol and water vapor is discharged. The dehydrated glycol then flows through a stripping column where glycol comes into contact with dry flue gas generated by a catalytic burner.
Anwar et al., U.S. Pat. No. 4,182,659, provides a system where wet glycol is initially drawn off into an expansion chamber where part of the hydrocarbon gases separate out, are drawn off and may be re-used as heating gas. The glycol is then heated to remove the majority of the water which is vented to the atmosphere. Finally, then glycol is heated at sub-atmospheric pressure (vacuum) to further purify it.
Holter, U.S. Pat. No. 4,003,722, discloses a system where gas may be purified by cleansing fluid. The cleansing fluid may be admitted from a flow circuit into an evaporator causing the impurities to be evaporated by heating. The impurities liberated in the evaporator are conveyed to a burner or combustion chamber and combusted.
The other previously issued patents provide information as to the state of the art of glycol dehydration of natural gas.
Accordingly, it is a principal object and purpose of the present invention to provide a system for control and disposal on contaminants released by natural gas dehydration processes.
It is further an object and a purpose of the present invention to provide a system for control and disposal of contaminants released in the glycol regeneration process wherein the contaminants are incinerated to reduce them to non-pollutant states.
It is further an object and a purpose of the present invention to provide a system for control and disposal of contaminants released in the glycol regeneration process which will not add undo back pressure to the reboiler.
The present invention relates to a system for use to incinerate contaminants released in the regeneration or reconcentration of glycol, or similar liquid desiccant, employed in the process of dehydration of natural gas.
Natural gas processing usually includes removal of contaminants in order to produce a transportable natural gas product. One of the major contaminants removed from natural gas is water, either in the gaseous state or in condensed form. Other contaminants present in smaller quantities are BTEX and VOCs and other pollutants.
Most large volume dehydration units are of the glycol type. Glycol is a preferred liquid desiccant because it has a relatively high boiling point, is thermally stable and does not oxidize in normal use. The glycol used is normally of one of three kinds: ethylene, diethylene, or triethylene, with triethylene being the most frequently used at the present time. Water, including other pollutants in natural gas, is absorbed by contact with the glycol.
A typical dehydration facility includes an inlet gas scrubber and a separator where liquid accumulations that are easily separated are removed. The natural gas is then directed to a gas contractor where the glycol comes into contact with the gas, a majority of any entrained water and the water vapor being absorbed by the glycol producing what is known as xe2x80x9cwet glycolxe2x80x9d. The dehydrated natural gas leaves the contractor tower where it is directed to be transported for use as fuel or raw material for the chemical industry. The wet glycol is directed from the contractor tower to a reconcentrator or reboiler column.
In the reboiler column the wet saturated glycol is heated to a temperature of between 380xc2x0 to 400xc2x0 Fahrenheit to boil off the water. The reboiler is usually maintained at the lowest possible pressure so that the water solubility of glycol is not increased. The vaporized water, along with the contaminants not removed with the skimming and filtration process, have, in the past, been vented to the atmosphere. Venting the contaminants to the atmosphere is becoming an increasing environmental problem. These odorous vapors emitted from the reboiler create uncomfortable living conditions and health concerns for local residents and workers.
New environmental laws have mandated a great reduction in the amount of pollutants that can be emitted from natural gas dehydrators. These pollutants consist primarily of BTEX and VOCs, and are absorbed from the gas stream by the glycol. Also, some natural gas becomes dissolved in the glycol, and since the function of a dehydrator is to remove water vapor from the gas stream, the glycol will also contain water. The glycol regeneration process utilizes a reboiler to heat the glycol and drive off the water, but the process also liberates the pollutants that are dissolved in the glycol. Current technology to control emissions consists of two methods: 1) The stream from the still column""s outlet is condensed. The waste gas is flared and the liquid is trucked to disposal. Or, 2) The stream from the still column""s outlet is condensed and the waste gas is compressed and injected into a gas sales line, the liquid, once again, being trucked to disposal. Obviously, the problem with both systems is dealing with the disposal of the BTEX and/or VOCs laden water. It is to this problem that the present invention is directed.